1. Field of the Invention
Fans, compressors, superchargers, blowers, and the like, all referred to herein generically as fans.
2. Brief Description of the Prior Art
Fans designed to provide either a high pressure, a high flow rate, or high output efficiency are typically large, heavy, thick-walled structures. Heavy construction is required to handle the air flows in high pressure and flow rate embodiments, and to permit sufficiently high rigidities and tolerances when high efficiency is desired to prevent significant efficiency loss through leakage or backflow between the fan impeller and housing.
Support frames have been utilized on the outsides of some prior art fans to reduce the weight and size needed to achieve desired strength, rigidity, and performance levels. But, unfortunately, external frames provide only limited support and moderate reduction in the weight and size required for a particular performance. Struts that run alongside housing walls are subject to bending moments and will not effectively offset those moments unless quite heavy construction is used. Struts that extend toward housing walls from a bearing flange or other base spaced from those walls so that the strut ends abut the housing at discrete points, are compressed by pressures inside the housing and thus require heavy bearing or other support bases. Furthermore, they provide support at only discrete positions. Thick walls or plates are thus often needed to offset strong bending moments between those support points.